Cutting Type and IBA Treatment Duration Affect Teucrium fruticans

Sabatino L. et al. / Not Bot Horti Agrobo, 2014, 42(2):478-481
Available online: www.notulaebotanicae.ro
Print ISSN 0255-965X; Electronic 1842-4309
Not Bot Horti Agrobo, 2014, 42(2):478-481. DOI:10.15835/nbha4229611
Cutting Type and IBA Treatment Duration Affect Teucrium fruticans
Adventitious Root Quality
Leo SABATINO, Fabio D’ANNA, Giovanni IAPICHINO*
University of Palermo, Department of Agricultural and Forest Sciences, Viale delle Scienze, 90128, Palermo, Italy; [email protected];
[email protected]; [email protected] (*corresponding author)
Abstract
Root development of stem cuttings of Silver Germander (Teucrium fruticans) was investigated in relation to cutting type
and indole-3-butyric acid (IBA) treatment. Terminal cuttings of a clone grown in Sicily were trimmed to three types: terminal
cuttings with apex (TWA), terminal cuttings without apex (TWOA) or sub-terminal cuttings (ST). To verify the cutting
response to exogenous auxin, cuttings were dipped to a 2.0 cm depth in a 0.5% indole-3-butyric acid solution for 0, 5 or 7
minutes. Overall percent survival was 97 to 98%. Rooting percent, root number and root length were affected by cutting type
and indole-3-butyric acid treatment. In general, TWA cuttings demonstrated a higher capacity to form roots than cuttings
without apex (TWOA and ST cuttings). In absence of indole-3-butyric acid treatment, TWA and ST cuttings gave higher
rooting percentages than TWOA cuttings. Exposing cuttings to indole-3-butyric acid improved percent rooting, number of
roots per cutting and root length. The best results in terms of rooting percentage and root number per cuttings were obtained
with TWA cuttings in combination with 7 min indole-3-butyric acid basal dip. However, cuttings taken farther down the
stem, such as sub-terminal cuttings gave satisfactory rooting performance as well. We suggest that the use of all cutting types
tested associated to indole-3-butyric acid basal dip for 5 or 7 min may be beneficial to propagators wishing to produce T.
fruticans rooted cuttings with well-developed root system.
Keywords: basal dip, growth regulators, Labiatae, native plants, rooting
Introduction
The genus Teucrium belongs to the family Labiatae and
contains more than 300 perennial herbs, shrubs and subshrubs mainly native to Mediterranean region and southwestern Asia (Bryant, 2003). Teucrium fruticans, also
known as Silver Germander, is a shrub native to Southern
Europe and North Africa (Graham, 1992). Cultivated for
its attractive blue/violet flowers and evergreen foliage, graygreen above and silver-white beneath, T. fruticans is high
drought tolerant and suitable for landscaping in areas with
Mediterranean-type environment (Cassaniti et al., 2009; La
Mantia et al., 2012; Lopez et al., 2006). Four-year old plants
(sold in 22-cm-diameter pots) obtained by rooted cuttings
are generally used for landscaping. Teucrium fruticans
propagation by seed is difficult because of poor germination
(Bryant, 2003) and high percentage of male sterility (Ojeda
and Dìez, 1992); as a result, plant propagation via seed is
unsatisfactory for the commercial production (Frabetti et
al., 2009). The species has been also characterized as
difficult to propagate by cutting in certain periods of the
year (Frangi and Nicola, 2004). To circumvent these
problems micropropagation has been recommended
(Frabetti et al., 2009). Vegetative propagation by stem
cuttings has been successfully applied to other Teucrium
species (T. divaricatum, T. polium, T. chamaedrys, T.
flavum, T. scorodomia) (Dirr and Heuser, 2006; Iapichino et
al., 2006; MacDonald, 1987; Maloupa et al., 2008).
Although the effects of exogenous auxin on adventitious
root formation in Teucrium species has been documented
(Dirr and Heuser 1987; Frangi and Nicola 2004; Maloupa
et al., 2008) no research on the influence of the
morphological characteristics of the cuttings on rooting of
T. fruticans has been reported. The aim of our study was to
examine rooting of stem cuttings in relation to cutting type
and IBA treatment duration in a T. fruticans clone grown in
Sicily.
Materials and methods
Plant material
The research was conducted at the University of Palermo,
Experimental Station in the Northern coast of Sicily (Italy)
(longitude 13° 19’ E, latitude 38° 9’ N). Terminal 30 cm long
stem cuttings were harvested on 23 April 2012 from actively
growing stock plants. Plants were 5 years old and from a single
Sicilian unnamed clone. Cuttings were stored overnight at
6 °C. The next day, the cuttings were trimmed to three types:
Sabatino L. et al. / Not Bot Horti Agrobo, 2014, 42(2):478-481
479
softwood stem-tip cuttings in which the tip was retained
(terminal cuttings with apex, TWA), softwood stem cuttings
in which the tip was removed (terminal cuttings without apex,
TWOA) or semi-hardwood cuttings taken farther down the
stem (sub-terminal cuttings, ST) (Fig. 1).
Fig. 1. Teucrium frutescens cutting types tested; from left,
terminal with apex, terminal without apex and sub-terminal
All cuttings were trinodal with the lower cut below a node
at the base of each cutting. Leaves were removed from the base
of the stem; length and diameter of the cuttings were 12-14 cm
and 0.4 cm, respectively.
Auxin treatment
To verify the cutting response to exogenous auxin, cuttings
were dipped to a 2.0 cm depth in a 0.5% indole-3-butyric acid
(IBA) solution (Frangi and Nicola, 2004) for five or seven
minutes. Reagent grade IBA (Sigma n. I 5386) was dissolved in
90% ethanol, then brought to final concentration of 6%
ethanol 94% distilled water (v/v). Untreated cuttings were
dipped in distilled water (control= 0 minutes).
Rooting conditions
Propagation was performed on 24 April 2012 in an
unheated greenhouse covered with clear polyethylene (PE) and
external 50% shade-cloth. Air temperature in the greenhouse
was 18-22 °C during the day and 14-16 °C during the night.
Cuttings were inserted 4 cm deep in a bottom heated bench
containing perlite. Basal heat was provided at constant
temperature of 25 ± 2 °C. Benches were covered with clear PE
to maintain high relative humidity. Intermittent mist operated
daily 30 sec every 2 hours from 8:30 AM to 6:00 PM.
Ventilation of the cuttings was increased with time by
increasing size of the holes made in the plastic.
Experimental design, data collection and analysis
The design was a randomized complete block (RCB) with
three replications, nine treatments [three cutting types x three
IBA exposure time duration (0, 5 or 7 minutes)] and 20
cuttings per replication. An IBA cutting exposition of a few
seconds (quick dip method) was not included in our
experimental design because in a preliminary experiment
(performed in the same season) we did not find any significant
increase in rooting capacity as compared to the untreated
control. After 4 and 6 weeks, cuttings were evaluated for
percent survival, percent rooting, number of roots, length of the
six longest roots. Cuttings with non-withered stems (with and
without roots) were considered to have survived. Cuttings with
necrotic tissue without roots were classified as dead. Percentage
data were subjected to arcsin transformation before ANOVA
analysis. Mean separation was performed by Fisher leastsignificant-difference test at p<0.01 (Petersen, 1985).
Plant establishment
Single plants were transferred to each plastic pot (diameter
16 cm) containing a peat-perlite mixture 1:1 (v/v) and kept for
five weeks in a lath house covered with 70% shade-cloth.
Acclimatized plants were thereafter transferred in the open
field.
The experiment was repeated a second year using the same
stock plants and obtaining similar results.
Results
Cutting survival and rooting percentage
Overall percent survival was 97 to 98%; no significant
effect of cutting type and IBA treatment duration was
found on cutting survival (Tab. 1). Rooting percent was
affected by cutting type and IBA treatment (Tab. 1). In
absence of IBA treatment, TWA and ST cuttings gave
higher rooting percentages than TWOA cuttings. Percent
rooting in TWA cuttings increased from 70% in absence of
IBA treatment to 100 and 96% in the presence of IBA for 5
and 7 min, respectively; percent rooting in TWOA cuttings
also increased from 56% in untreated control to 100% in
cuttings receiving either 5 or 7 min IBA basal dips. Percent
data recorded on ST cuttings paralleled data recorded on
TWA and TWOA cuttings exposed to IBA giving higher
performance than control.
Fig. 2. Teucrium frutescens cuttings in the rooting bench
Root number
The number of roots was affected by cutting type and
IBA treatment. In general, TWA cuttings demonstrated a
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higher capacity to form roots than cuttings without apex
(TWOA and ST cuttings). Exposing cuttings to IBA
improved the number of roots per cutting (Fig. 2). Data
collected 4 weeks after planting revealed that formed roots
on TWA cuttings increased from 1.0 in untreated control
to 14 and 18 roots on stem cuttings receiving 5 and 7 min
IBA basal dips, respectively. Root count in TWOA cuttings
also increased from 1.5 roots in absence of IBA to 11 roots
at 5 min duration and to 20 roots at 7 min duration. Data
collected on ST cuttings supported the trend established for
the other two cutting types with a maximum of 13 roots for
the cuttings receiving 7 min IBA basal dip. Data collected
Tab. 1. Effects of cutting type and IBA treatment on Teucrium fruticans rooting
Treatments
Roots per cutting (n)
Root length (mm)
Rooting (%)
Survival (%)
6
6
6
Cutting type
IBA
(min.)
Weeks after planting
TWA
0
1.0 ± 0.8 e
11.4 ± 4.2 d
3.5 ± 1.6 de
6.8 ± 2.5 e
70 ± 0.3d
97.0 ± 1.3 a
TWA
5
14.7 ± 3.8 b
18.4 ±3.9 bc
5.9 ± 0.5 ab
10.1 ± 3.9 abc
100 a
98.0 ± 2.8 a
TWA
7
18.5 ± 3.3 a
24.0 ± 3.6 a
4.7 ± 1.8 bcd
11.5 ± 4.1a
96 ± 2.8ab
97.1 ± 2.5 a
TWOA
0
1.5 ± 0.7 e
4.0 ± 2.4 e
2.5 ± 0.8 e
5.3 ± 2.8 f
56 ± 2.1e
98.0 ± 2.1 a
TWOA
5
11.0 ± 4.2 cd
14.3 ±2.5 d
7.0 ± 1.0 a
10.5 ± 4.1 ab
100 a
98.0 ± 1.8 a
TWOA
7
20.1 ± 1.5 a
20.2 ± 2.1ab
5.0 ± 2.1 abc
9.3 ± 2.1bcd
100 a
97.6 ± 2.8 a
ST
0
1.9 ± 0.6 e
6.1 ± 2.6 e
2.6 ± 1.2 e
5.0 ± 2.7 f
81 ± 3.4cd
98.0 ± 3.6 a
ST
5
9.7 ± 2.9 d
13.1± 4.7 d
3.2 ± 0.9 de
7.8 ± 3.2 e
100 a
98.0 ± 2.0 a
ST
7
13.0 ± 1.8 bc
15.0 ± 2.2 d
4.2 ± 1.6 cd
7.7 ± 3.1 e
92 ±1.7abc
97.6 ± 2.5 a
4
6
4
Values represent mean ± standard error. In each column, means followed by the same letters are not significantly different at the p < 0.01% level by Fisher’s protected least
significant difference test.
TWA = terminal cuttings with apex; TWOA = terminal cuttings without apex; ST = sub-terminal cuttings.
after 6 weeks again revealed that rooting TWA, TWOA
and ST cuttings in the presence of IBA substantially
increased the number of roots per cutting as compared to
untreated cuttings. All cutting types generally produced
higher number of roots per cutting with 7 min IBA basal
dip as compared with 5 min IBA basal dip. Among the
treatments tested, TWA cuttings in combination with 7
min IBA basal dip was the most effective in terms of
number of adventitious roots produced.
Root length
Root length also varied by cutting type and IBA
treatment. Generally, TWA cuttings formed longer roots
than cuttings without apex (TWOA and ST cuttings).
Data collected four and six weeks after planting, revealed
that root length increased from the untreated control to
stem cuttings receiving IBA basal dips. However, no
significant differences were found between 5 and 7 min IBA
basal dip.
Plant establishment and performance
In the present study, propagated plants grew vigorously,
were morphological normal and began to flower during
spring 2013.
Discussion
Fig. 3. Teucrium frutescens sub-terminal cuttings, exposed to 7
min IBA basal dip, showing a well developed rooting system
Our results are similar to those of Krisantini et al.
(2003) who report tip cuttings having a higher capacity to
form roots than decapitated cuttings in Grevillea and are
consistent with those of Marks (1996) who found
inhibition of rooting following tip removal in Quercus and
Daphne cuttings. The higher rooting percentage obtained
using tip cuttings rather than stem (decapitated) cuttings
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481
has been hypothesized as due to production of a factor
(presumably, IAA basipetally transferred from the
meristems) that from the apex has an important role in
adventitious root formation even though exogenous auxin is
applied. In our study, the slightly higher, but not statistically
different percentage rooting observed in ST cuttings as
compared to TWA cuttings could be attributed to the fact
that IAA was supplied from quiescent axillary buds.
However, our study also demonstrated that the number of
roots formed in cuttings with apices was superior to that
observed in those without apices even in the presence of
exogenous auxin.
In our study, the application of IBA improved rooting
percentage and root number as compared to untreated
control. IBA has been reported to markedly increase
adventitious root formation in many species (Blazich, 1988;
De Klerk et al., 1999; Hartmann et al., 1997). Our results
are only partially in agreement with those obtained by
Frangi and Nicola et al. (2004) who found IBA treatments
enhancing rooting in T. fruticans stem tip cuttings. These
authors report a low rooting response during spring (40%
rooting) even applying exogenous auxin. Our higher
response in the same season could be related to diverse
genotype studied or different environmental conditions
under which the stock plants were grown. Our results are in
accord with the results obtained by Carpenter and Cornell
(1992) who, investigating the adventitious root
proliferation response of three Hibiscus rosa-sinensis
cultivars, found that rooting is highly influenced by IBA
application duration and concentration. Our results are also
consistent with those of Telgen et al. (2007) who reported
that diluted IBA-solutions and longer dipping times
resulted in more uniform cuttings and higher root number
than quick dips in Rosa hybrida ‘First Red’.
In the present study, the best results in terms of rooting
percentage and root number per cuttings were obtained
with TWA cuttings. However, this propagation method
yields fewer cuttings per plant compared with methods
using cuttings taken farther down the stem, such as subterminal cuttings which, in our study, also performed well.
Therefore, we suggest that all cutting types tested and
exposed to an IBA basal dip of 5 or 7 min may be
successfully used by propagators to produce T. fruticans
rooted cuttings with well-developed root system.
This is an important information for nursery growers
since there is little knowledge about cultural techniques of
this species of increasing importance in the landscape and
nursery trade.
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